Evaluating the swelling, erosion, and compaction properties of cellulose ethers

Abstract

Swelling, erosion, deformation, and consolidation properties can affect the performance of cellulose ethers, the most commonly used matrix former in hydrophilic sustained tablet formulations. The present study was designed to comparatively evaluate the swelling, erosion, compression, compaction, and relaxation properties of the cellulose ethers in a comprehensive study using standardised conditions. The interrelationship between various compressional models and the inherent deformation and consolidation properties of the polymers on the derived swelling and erosion parameters are consolidated. The impact of swelling (K_w) on erosion rates (K_E) and the inter-relationship between Heckel and Kawakita plasticity constants was also investigated. It is evident from the findings that the increases in both substitution and polymer chain length led to higher K_w, but a lower K_E; this was also true for all particle size fractions regardless of polymer grade. Smaller particle size and high substitution levels tend to increase the relative density of the matrix but reduce porosity, yield pressure (P_y), Kawakita plasticity parameter (b⁻¹) and elastic relaxation. Both K_W versus K_E (R² = 0.949–0.980) and P_y versus. b⁻¹ correlations (R² = 0.820–0.934) were reasonably linear with regards to increasing hydroxypropyl substitution and molecular size. Hence, it can be concluded that the combined knowledge of swelling and erosion kinetics in tandem with the in- and out-of-die compression findings can be used to select a specific polymer grade and further to develop and optimize formulations for oral controlled drug delivery applications.

Keywords:

• Methylcellulose
• hypromellose
• hydrophilic matrices
• matrix swelling
• matrix erosion

Acknowledgements

The authors acknowledge Colorcon, UK, for providing gift samples of Methocel^®.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors acknowledge the financial support provided by the University of Huddersfield, Huddersfield, UK.